Bypass flow and ozone proportion method and system

ABSTRACT

A method and system of ozone treatment diverts a portion of water from a flow of water in a conduit; injects an ozone-containing gas into the portion to provide an ozonated portion; recombines the ozonated portion with the flow of water in the conduit; and regulates the diverted portion to provide a minimum diverted portion flow rate according to flow in the conduit and proportion of ozone in the injected gas.

This application is a continuation-in-part application of U.S.application Ser. No. 11/039,819, filed Jan. 24, 2005, now U.S. Pat. No.7,273,562, which in turn is a continuation-in-part of U.S. applicationSer. No. 10/402,298, filed Mar. 31, 2003, now U.S. Pat. No. 6,869,540,which claims the benefit of U.S. Provisional Application Ser. No.60/372,806, filed Apr. 17, 2002 , all the disclosures of which areincorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

The invention relates to a ballast water ozone injection method andsystem. More particularly, the invention relates to a system forinjecting ozone to treat water during loading or discharge to or fromthe ballast tanks of a vessel or ship.

Ballast water weight is used by sea vessels to compensate for a lack ofcargo weight to maintain stability when the ship cargo hold is empty orpartially empty. For example in a typical transport operation, a vesseldocks at a first port where it is loaded with a cargo that is transportsto a second port where the cargo is unloaded. The vessel then returns tothe first port where it is loaded with another cargo. Typically, thevessel travels empty from the second port back to the first port to pickup another cargo. The vessel is equipped with ballast tanks that can befilled with water to maintain the balance of the vessel when it travelsempty and that is discharged as cargo is loaded.

Ballast water contains species that are indigenous to the ballast tankfilling location. These species are loaded into the ballast tanks alongwith the water. The vessel then transports ballast water to a cargoloading port where the species are discharged into the water environmentalong with the ballast water. The discharged species may benonindigenous and deleterious to the discharge water environment. Thenonindigenous species may cause damage to the water environment andreplace benthic organisms and clear plankton communities that providefood and larvae for desirable resident native species.

In 1996, Congress passed the National Invasive Species Act (P. L.104-332) (“NAIS”) to stem the spread of nonindigenous organisms throughballast water discharge. The act reauthorized the Great Lakes ballastmanagement program and expanded applicability to vessels with ballasttanks. The Act requires the Secretary of Transportation to developnational guidelines to prevent the spread of organisms and theirintroduction into U.S. waters via ballast water of commercial vessels.The National Aquatic Invasive Species Act and the Ballast WaterManagement Act and pending or to be introduced legislation regulate thetreatment of salt or fresh ballast water prior to its discharge andwould require that all ballast water discharged within the territorialwaters of the United States (i.e. within 200 miles of the Coast or inthe Great Lakes) be treated so as to kill or remove all aquatic nuisancespecies (i.e. bacteria, viruses, larvae, phytoplankton and zooplankton).

The water loaded into ballast tanks is a complex composition ofphysical, chemical and biological entities. Further, the composition ofthe water varies considerably from port to port, particularly in termsof biological constituents. The complexity and variation of the watermakes disinfectant treatment unpredictable. Various known methods andsystems for treating water may not work for treating ballast waterbecause of a resistant life form or unexpected chemical constituency ora proposed treatment itself may degrade a local ecosystem upondischarge.

Ozonation has been found to be a safe and effective disinfectant methodand system to treat ballast water for discharge into destination waterenvironments. Rodden U.S. Pat. No. 6,125,778 first suggested an ozoneballast water treatment that included sparging into ballast water tanks.

However direct tank sparging may make ozonation disinfection expensiveand ineffective as not all spaces in ballast tanks may be reached.Robinson et al. U.S. Pat. No. 6,869,540 (Robinson) has suggested anin-line treatment of loading and/or unloading ballast water. TheRobinson method can comprise injecting ozone into a line of waterloading into a sea faring vessel prior to charging the water into aballast tank; charging the ozone injected water into the ballast tank;and adjusting a rate of injection of the ozone into the water andadjusting the rate of water loading into the vessel to provide a targetbiokill of species within the water.

Robinson ozonation achieves disinfection by a sequential and combinedtwo mechanism effect—ozonation and bromination. Ozone directly killsspecies by oxidation. Additionally, a reaction between ozone andnaturally occurring seawater bromides results in a disinfectingbromination through the formation of hypobromous ion and hypobromousacid. The effect of the ozonation and bromination disinfecting processeshas been found to be synergistic in that the combined effect is animprovement over the effects of the separate disinfectant processes.While in-line ozonation of seawater during pumping intake or dischargeis more effective and more economical than in-tank treatment, in someinstances there are serious cost restrictions on direct ozonation. Forexample, ballast water intake/discharge lines on vessels in the 100,000to 150,000 DWT range are 18″ in diameter. The cost of equipment fordirect injection into this size line is prohibitive. There is a need foran uncomplicated and cost effective system and method for directozonation of intake/discharge ballast water.

BRIEF DESCRIPTION OF THE INVENTION

A first aspect of the invention is a method of ozone treatment,comprising: diverting a portion of water from a flow of water in aconduit; injecting an ozone-containing gas into the portion to providean ozonated portion; recombining the ozonated portion with the flow ofwater in the conduit; and regulating the diverted portion to provide aminimum diverted portion flow rate according to flow in the conduit andproportion of ozone in the injected gas.

In an embodiment, the invention is a water treatment system comprising:a water conduit that transports water from a first intake location to adischarge location; a bypass line from a first point of the waterconduit to a second, return point wherein the bypass line diverts aportion of the water from the conduit for circulation in the bypass lineand back to the water conduit at a return point; an injector included inthe bypass line to inject ozone into the diverted portion of water; anozone generator that generates ozone for injection by the injector; anda regulator that regulates the diverted portion to provide a minimumdiverted portion flow rate according to flow in the conduit andproportion of ozone in the injected gas.

And in another embodiment, the invention is a method of ozone treatment,comprising: uploading seawater to a ballast tank of a sea faring vessel;regulating a diverted portion of the uploading water prior to chargingthe water into the ballast tank; and adjusting the regulating of thediverted portion of water and a rate of injection of ozone into theportion to provide a minimum diverted portion flow rate according toflow in the conduit and proportion of ozone in the injected gas.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic perspective view of a double hulled vessel andtreatment system;

FIG. 2 is a schematic side view of the vessel and treatment system;

FIG. 3 is a schematic top view of the vessel and treatment system;

FIG. 4 is a flow diagram of a method and system for ballast water ozoneinjection; and

FIG. 5 is a schematic side view of a bypass conduit system.

DETAILED DESCRIPTION OF THE INVENTION

Ozone is generated at a pressure of about 10-12 psi above atmospheric.Deviations from this pressure may adversely affect ozone output. Ballastwater is pumped aboard at variable pressure, which may be high as tanksare filled. Relatively low-pressure ozone/oxygen or ozone/air mixturescan be compressed to a higher pressure by very special and expensiveequipment (due to the corrosivity of ozone and more importantly, thefact that ozone will decompose under the heat of compression).

In an embodiment, the invention relates to ozone ballast watertreatment. Proposed NAIS amendments define “ballast water” as “any water(with its suspended matter) used to maintain the trim and stability of avessel.” In another definition, “ballast water” is A) water taken onboard a vessel to control trim, list, draught, stability or stresses ofa vessel including matter suspended in such water; and B) any waterplaced in a ballast tank during cleaning, maintenance or otheroperations.” These definitions are incorporated into this specificationas embodiments of treatable water.

In an embodiment of the invention, an inline gas injector such as aventuri is interposed to temporarily lower pressure of flowing ballastwater by increasing the velocity of the water flow in a conduit. Aninterposed inline injector can create a lower pressure by increasingliquid velocity. A venturi is a preferred injector in an inlineinjection ballast water treatment.

In an embodiment, the invention relates to a ballast water treatmentsystem for a vessel. The system can comprise an injector interposed in awater conduit with an inlet port adapted to receive the water, aninjector port adapted to receive a treating gas and an outlet portadapted to expel the water. However, ballast water conduits that chargewater to or discharge water from a ballast tank are large, typically onthe order of about 18 inches in diameter. The cost of an injector suchas a venturi for a conduit of this size is substantial. Further,installing such an injector into a main conduit will impact operationalparameters of the vessel. An interposed injector will increase flowbackpressure and require an increased ballast water pump capacity.Applicants' calculations indicate that an interposed venturi willincrease a pumping time required to fill ballast tanks of some vesselsby one or two hours (about 10%). Further, ballast water conduits mayserve both to load ballast water and to discharge ballast water. Aninterposed injector may interfere with a reversed water flow, forexample to discharge ballast water. These disadvantages can be overcomeby a preferred embodiment of the invention wherein ozone is injectedinto a portion of ballast water in a line that bypasses a part of themain water conduit.

A further preferred embodiment of bypass line ozone injection is basedon consideration of the physical and chemical nature of ozone in ballastwater including the solubility of ozone in seawater and the relationshipof the chemical reactions of the ozone to solubility.

Ozone (O₃) is an allotropic form of oxygen. It is an unstable blue gaswith a pungent odor, a molecular weight of 48 g/mol and a density as agas of 2.154 g/liter at 0° and 1 atm. It is approximately 13 times moresoluble in water than is oxygen. Ozone is highly unstable and is apowerful oxidizing agent. It is non-persistent and has a very shorthalf-life.

Typically, ozone is produced by passing oxygen, in some concentration,through a highly charged corona field, a technique known as “coronadischarge”. The corona may be produced by applying a very high electricpotential (up to 20 kV) between two conductors that are separated by aninsulating dielectric layer and a small air gap. Under these conditions,molecular oxygen (O₂) passing through the gap between the conductorsexperiences sufficient dissociation energy to partially dissociate. Acertain fraction of the free oxygen radicals will associate with oxygenmolecules to form O₃, according to the equilibrium reaction equation:3O₂+69 kcal

2O₃  (I)

The generation of ozone as represented by equation (I), is anequilibrium reaction. The reaction is endothermic to produce O₃,requiring energy, and is exothermic to produce O₂, giving up energy.Because of its equilibrium nature, actual conversion to ozone isrelatively low, in the range of 2-14%, depending on the oxygen contentof feed gas, the temperature of the reaction and properties of the ozonegenerator.

Other considerations in providing an effective ozone treatment methodand system relate to the mechanism of gas treatment of ballast water.McNulty, U.S. Pat. No. 6,840,983 discloses a ballast water treatmentsystem that comprises an injector interposed in a main water conduitwith an inlet port adapted to receive the water, an injector portadapted to receive an oxygen stripping gas and an outlet port adapted toexpel the water. McNulty injects an oxygen stripping gas that scavengesoxygen from the ballast water purported to cause suffocation ofoxygen-dependent species. On the other hand, ozone is an oxidizing gasthat has different and at least double disinfecting mechanisms. Thesemechanisms include rapid conversion of naturally occurring ballast waterchemical constituents into products that are toxic to organisms as wellas direct ozone destructive oxidation of organisms.

The following four equations (Von Gunten & Hoigné, 1994) describe theutilization of ozone in seawater assuming the only ozone demand isbetween ozone and dissolved bromide.

(1) O₃ + Br⁻ → OBr⁻ + O₂ 160 M⁻¹s⁻¹ (2) OBr⁻ + O₃ → 2O₂ + Br⁻ 330 M⁻¹s⁻¹(3) OBr⁻ + O₃ → BrO₂ ⁻ + O₂ 100 M⁻¹s⁻¹ (4) BrO₂ ⁻ + O₃ → BrO₃ ⁻ >10⁵M⁻¹s⁻¹

Hypobromous ion (OBr—) is created in reaction (1). Most of the reaction(1) ion is then converted to hypobromous acid (HOBr) by addition of ahydrogen ion from water. The hypobromous ion and hypobromous acid formedare known as total residual oxidant (TRO). Only reaction (1) leads tothe formation of TRO. The further reactions (2) to (4) undesirablyremove both ozone and bromine products from the disinfectant process. Afirst goal of seawater ozonation is to convert as much ozone as possibleto HOBr or OBr⁻. Therefore, maximizing reaction (1) and minimizingreactions (2)-(4) will maximize OBr⁻.

The reactions shown are of second order. The given reaction rateconstants indicate the speed at which the reaction occurs as a functionof the ozone concentration. To determine a relative rate betweenreactions (1) and (2), the rate constant of (2) is divided by that of(1). The rate of reaction (2) is approximately 2 times faster thanreaction (1)—that is for equal concentrations of the reactants.

The above reaction rates are such that if the molar concentration ratioof Br— to OBr— drops below about 2.7, further ozone dosages do notproduce more OBr— as the ozone consumption in reactions (2) and (3) willexceed reaction (1). The hypobromous ion forming reaction dominates whenozone is introduced into an excess of bromide. Typically about 70 mg/Lof bromide is available in seawater. This provides enough bromide excessto minimize ozone losses at typical ozonation levels (1 to 5 mg/L ofozone) into a conduit of loading or unloading ballast water. However, abypass line will present a lesser amount of water and a correspondinglesser amount of bromide available to be used up before dominance of theozone and OBr⁻ dissipation reactions (2) to (4).

The available amount of bromide in bypass seawater needs to be takeninto consideration when determining a flow rate or retention time forbypass ozonation. Retention time is a period for transport of ozone andwater from a point of injection of the ozone to reinjection of bypasswater and ozone into a main conduit. In an embodiment, a method andsystem are provided whereby dissipating ozone and OBr⁻ reactions areminimized while the synergistic disinfection by ozonation andbromination is maintained. According to an embodiment of the invention,a method and system are provided to minimize retention time. In thisspecification, retention time is a period of time from injection ofozone into water in a bypass to reinjection time of the bypass lineseawater into the seawater of a main conduit or tank. An embodiment ofthe invention provides for reinjecting an ozone treated bypass waterportion back into a “bromide rich” main conduit seawater to avoidsubstantial ozone and OBr⁻ consumption in BrO₂ ⁻ and BrO₃ ⁻ formationand oxygen reversion per reactions (2) to (4). “Retention time” isminimized.

In an embodiment, a 0.21 second retention time results in an acceptable4.3% ozone loss. According to an embodiment of the invention, a methodand system are provided wherein retention time is controlled at lessthan 5 seconds, desirably less than 0.25 seconds and preferably lessthan 0.21 seconds to minimize reactions (2) to (4).

Features of the invention will become apparent from the drawings andfollowing detailed discussion, which by way of example withoutlimitation, describe preferred embodiments of the invention.

FIGS. 1 to 3 schematically show vessel 10 including stern 12, bow 14 anda double hull formed from outer hull 16 and inner hull 18. Vessel 10 isrepresentative of the types of vessels encompassed within the inventionand is a conventionally proportioned double-hulled oil tanker havingcargo compartments within inner hull 18. However, the present inventioncan be applied to any sea faring ship or vessel that has ballast tanksor bilge water. The vessel 10 is typical of vessels that transportpartly or fully refined or residual petroleum or other bulk liquidproducts such as seed oil.

Ozone generator 30 is illustrated located on vessel 10 aft deck 102 withmain ozone feed line 130 shown as part of the ozone injection system ofthe invention. Generator 30 can be structured and can generate ozoneaccording to known ozone generators such as described by Rodden U.S.Pat. Nos. 6,125,778; 6,139,809; and PCI-WEDECO (PCI-WEDECO EnvironmentalTechnologies, 1 Fairfield Crescent, West Caldwell, N.J. 07006) typeSMO/SMA series generators and WEDECO Effizon® technology highconcentration ozone production generators as examples. The disclosuresof these patents are incorporated herein by reference in their entirety.

Ozonated gas is pumped through generator 30 and subsequently throughline 130 for injection into water in respective ballast waterintake/discharge conduits 116, 118 and 120 via respective connectorlines in accordance with the FIGS. 1 through 3 embodiment of theinvention. See also connector lines 110, 112 and 114 of FIG. 4A of U.S.Pat. No. 7,273,562. Intake/discharge conduit 116 conveys water from stemintake/outlet sea chest 132 to forward battery 124 of ballast tanks.Intake/discharge conduit 118 conveys water from starboard intake/outletsea chest 134 to a starboard battery 126 of ballast tanks.Intake/discharge conduit 120 conveys water from port intake/outlet seachest 136 to a port battery 128 of ballast tanks.

Ballast water is loaded into the vessel 10 via the sea chests 132, 134,136 and is then pumped to load respective ballast tank batteries 124,126, 128 through the system of conduits 116, 118 and 120 shown. At adestination location, the process is reversed and water is pumped fromtank batteries 124, 126, 128 through the respective conduits 116, 118,120 for discharge through respective sea chests 132, 134, 136 to thesea. Or, discharge can be effected through another, separate conduit andsea chest system (not shown) from tank batteries 124, 126, 128. Afterinjection with ozone, the water is conveyed by one of the main conduits116, 118, 120 to respective tank batteries 124, 126, 128. As each mainconduit 116, 118, 120 passes through each ballast tank 124, 126 or 128,a smaller footer pipe (not shown) can be taken off to provide asuction/discharge conduit. Valving for the footer pipe can be containedin a tunnel or cofferdam area, or actually placed in the tank itself, ifspace is an issue.

In FIGS. 2 and 3, conduit 118 delivers ozone treated water to eachballast tank of a starboard battery of tanks 126 and conduit 120delivers ozone treated water to each ballast tank of a port battery oftanks 128. Water enters through respective sea chests 134 and 136 and istreated and charged into a tank of either the starboard battery 126 orthe port battery 128 until each respective tank is sufficiently filledand balanced to compensate for off-loaded cargo. Similarly, as shown inFIGS. 2 and 3, water enters through stem sea chest 132, is treated withozone and charged into a tank of forward battery 124 until each tank isfilled to balance the vessel 10.

FIG. 4 is a flow diagram of an embodiment of a method and system forballast water ozone injection that can be used in conjunction with thesystem of vessel 10 shown in FIGS. 1 to 3. In FIG. 4, ozone generationsystem 502 includes air compressor 514, refrigerated air dryer 516,coalescing filter 518, air receiver 520, O₂ enricher 522, O₂ receiver524, dew point monitor 526, filter 528, ozone generator 530, powersupply 532, ozone monitor 534, ozone destruct unit 536 and chiller 538with circulation pump 540. In operation, air is drawn into the system502 via air intake 512. The air is compressed 514, dried andrefrigerated 516, filtered 518 and temporarily stored in 520. Thenaccording to generator demand, air is withdrawn to enricher 524, whereoxygen content of the gas is increased by adsorption of nitrogen. Oxygenenriched gas is delivered to receiver 524, monitored 526 and filtered528 until injected into ozone generator 530 operated via power supply532. Off-gas from generator 530 is monitored 534, and destroyed 536 toprevent environment discharge. Generated ozone is stored at chiller 538until demanded by bypass injection systems 550, 552, 554 as hereinafterdescribed.

FIG. 4 shows three separate injection systems 550, 552, 554, which cancorrespond respectively to injection into aft intake conduit 116,injection into starboard intake conduit 118 and injection into portintake conduit 120. Injection system 550 includes ozone regulator 560,which can be a pump to regulate flow in the bypass 594. Further, theinjection system 550 includes ozone injector 564, static mixer 566 andreinjector 568. Similarly injection system 552 includes regulator 570,ozone injector 574, static mixer 576 and reinjector 578 and injectionsystem 554 includes regulator 580, ozone injector 584, static mixer 586and reinjector 588. Injection systems 550, 552 and 554 are controlledrespectively by controllers 610, 612 and 614. Controller 610, 612 and614 can be a processor, computer or microprocessor or the like forregulating bypass flow and controlling injected ozone as hereinafterdescribed.

FIG. 5 schematically shows detail of bypass injection of ozone into adiverted portion of water loading to or unloading from a ballast tank.The bypass injection allows for ozone injection, provides proper mixingand solubilization of the ozone gas into the ballast water and properremixing of the ozonated diverted portion with the main water flow.Shown in FIG. 5 is exemplary aft load/discharge bypass injection system550. The system 550 includes a bypass conduit 594 that diverges frommain conduit 116 at an upstream point 622 and reconverges with the mainconduit 116 at a downstream point 624. Bypass conduit 620 includes pump560, venturi 564, mixer 566 and main conduit reinjector 568.

Taking system 550 as an exemplary system, operation is described asfollows: Seawater from sea chest 132 (FIG. 4) is fed in conduit 116 viamain ballast water pump 592 (FIG. 4) to injection system 550. A portionof the seawater is diverted by circulation pump 560 from conduit 116into by-pass line 594. Flow of the diverted water portion is controlledby regulating the pump 560. Injector 564 injects ozone from generator530 into the diverted seawater portion. The ozone injector 564 can be aventuri injector or the like. The injected ozone is dispersed furtherinto the seawater portion by static mixer 566 and combined back with themain seawater in conduit 116 at mainline contactor 568.

The injector 564 can be any gas into fluid injector such as a jetinjector, but preferably is a venturi to address the requirements ofmixing gas into a high volume of liquid to achieve a high degree ofsolubility. Further, a venturi is desirable because of its very lowpower consumption, few moving parts, and minimal system backpressure. Aventuri works by forcing a fluid through a conic constriction thatinitiates a pressure differential in the venturi tube between an inletand an outlet port. The pressure differential inside the venturi tubeimitates suction of another fluid (ozone containing gas in the presentcase) through a port of an intersecting side line.

A venturi injector can include a venturi tube that comprises a shortstraight pipe section or throat between two tapered sections. Thetapered sections form the constriction that causes a drop in pressure asfluid flows through the pipe. The pressure drop draws ozone into theflow from the intersecting side line.

The ozone gas/water mixture can be processed through a static mixer 566after exiting the venturi injector. Mixer 566 is a static mixer thatprovides additional solubilization of ozone into the water and ensuresthat entrained ozone gas bubbles are uniformly dispersed in the bypassconduit water. Mixer 566 can be any suitable mixer but a static mixer ispreferred. Typically, a static mixer comprises a series of fins,obstructions, or channels mounted or fixed into a piping arrangement.The fins, obstructions or channels are designed to promote furthermixing of the ozone gas and ballast water liquid. A static mixer may usesome method of first dividing the flow, then rotating, channeling, ordiverting it. The static mixer intensifies the physical and chemicalprocesses of ozone solubilization. The intensified mixing lengthens thedistance covered by gas bubbles and breaks the bubbles into stillsmaller bubbles thereby increasing the ability to transfer ozone fromthe gas mixture to the water. The mixer of the system can provide anadditional 5-10% solubilization.

The static mixer 566 is selected by considering the material to beprocessed and the rate at which it must be processed. A static mixerwith at least 12 elements or equivalent composite mixer can be used tofit a pipe of the same diameter as that exiting from the injector. Inaddition, allowable pressure drop must be assessed, in order to makecertain that the bypass circulating pump has both flow capacity andpressure capability to provide proper mixing in the static mixer. Also,the water flow rate should be high enough to ensure a low enough contacttime to minimize ozone losses to wasteful by reactions in seawater.

According to an aspect of the invention, a minimum bypass flow rate isrequired to provide sufficient ozonation of ballast water when thebypass is reinjected back into a main conduit. In an embodiment, aminimum bypass flow rate must be maintained of at least 0.25% of themain conduit flow for every mg/L of ozone injected into the bypass.Desirably the bypass flow rate is maintained at more than 0.30% of themain conduit flow and preferably, the flow rate is maintained at 0.35%of the main conduit flow. For example as described hereinafter for0.33%, a flow ratio between a bypass flow and that in the main conduitflow is about 66 gal/min to 10,000 gal/min. In operation for example,controller 610 controls pump 560 to regulate water flow in coordinationwith ozone injection by injector 562 to effectively provide a minimumdiverted portion flow rate according to flow in the conduit andproportion of ozone generated in the injected gas. Thus the controller610 can coordinate flow by pump 560 with injector 564 to providediverted portion flow of at least 0.25% of a main conduit flow for everymg/L of ozone injected into the bypass.

The following examples serve as illustrations and are not intended aslimitations of the present invention as defined in the claims.

EXAMPLE I

In this EXAMPLE, ballast water is fed from an intake/discharge conduitbetween a sea chest and a battery of ballast tanks of a 100,000 to150,000 DWT tanker. The water is fed at a 10,000 gpm flow rate. Theseawater contains 70 mg/L of bromide.

A bypass stream of water is diverted from the intake/discharge conduitat a constant flow into a bypass conduit system illustrated in FIG. 5.Ozone gas is fed under slight pressure (12-15 psi) from its generatingsource through 316L stainless steel piping to a venturi injector. Theozone is injected as a 10-12% ozone in oxygen admixture. A bypass flowrate is set to permit effective injection by the venturi. In thisEXAMPLE, a bypass flow rate is set at 66 gpm and pressure ofapproximately 90 psi. This flow rate is 0.3% of the main flow for everymg/L of ozone to be dosed (2.0 mg/L in this EXAMPLE). Flow and pressureare maintained by a positive displacement pump.

The selected flow rate and pressure are confirmed as follows: The flowratio between the main flow and that in the bypass is about 10,000gal/min to 66 gal/min. The specific ozone dosage in the bypass toachieve 2 mg/L in the main stream would be 303 mg/L so that with only 70mg/L of bromide in the seawater, OBr⁻ would exceed Br⁻ by far, favoringthe undesirable reactions. The beneficial reactions producing OBr⁻ willonly dominate once the bypass stream is remixed with the main stream.Hence, bypass retention time is minimized to avoid as much ozone loss aspossible and to meet the main dosage requirement of 2.0 mg/L.

The bypass injection venturi minimizes back-pressure and provides 90-95%solubilization of ozone gas in seawater.

EXAMPLE II

In this EXAMPLE, bypass piping length for the bypass 594 is limited anda higher than typical pumping rate is maintained to reduce retentiontime down to almost 0.2 seconds as follows:

A bypass flow rate of 66 gpm typically requires a 2″ pipe size. In thisEXAMPLE, a smaller pipe size is selected to improve the flow velocity.Since back pressure on the venturi is also a limitation, the selectedpipe size is decreased by only one size increment, i.e. to 1½″. Thecross-sectional area of a 1½″ Schedule 80 pipe is 0.01227 square feet.The flow rate is (66/(7.48×60))=0.1471 ft³/sec, so that the velocity inthe pipe is increased to 0.1471/0.01227=12 ft/sec.

The bypass system is designed to provide a minimum length (retentionlength) from venturi to main conduit reinjection point as follows. Theretention length is limited to a first 15 nominal diameters length toaccommodate a static mixer and an additional 30 inches to accommodate anangled reinjector. The retention length for these requirements is 2.5feet. The resulting retention time in traveling 2.5 ft at 12 ft/sec=0.21s.

While preferred embodiments of the invention have been described, thepresent invention is capable of variation and modification and thereforeshould not be limited to the precise details of the EXAMPLES. Theinvention includes changes and alterations that fall within the purviewof the following claims.

1. A water treatment system comprising: a water conduit that transportswater from a first intake location to a discharge location; a bypassline from a first point of the water conduit to a second, return pointwherein the bypass line diverts a portion of the water from the conduitfor circulation in the bypass line and back to the water conduit at areturn point; an injector included in the bypass line to inject ozoneinto the diverted portion of water; an ozone generator that generatesozone for injection by the injector; and a regulator that regulates thediverted portion to provide a minimum diverted portion flow rateaccording to flow in the conduit and proportion of ozone in the injectedgas.
 2. The system of claim 1, wherein the regulator regulates thediverted portion to at least 0.25% of the main conduit flow for everymg/L of ozone injected into the bypass.
 3. The system of claim 1,wherein the regulator regulates the diverted portion to at least 0.3% ofthe main conduit flow for every mg/L of ozone injected into the bypass.4. The system of claim 1, wherein the regulator regulates the divertedportion is to at least 0.35% of the main conduit flow for every mg/L ofozone injected into the bypass.
 5. The system of claim 1, furthercomprising a static mixer located within the bypass conduit downstreamto the injector.
 6. The system of claim 1, comprising a mixer locatedwithin the bypass conduit downstream to the injector; and a reinjectorto reinject the diverted portion with ozone back to the water conduit atthe return point.
 7. The system of claim 1, comprising a plurality ofinjectors to inject ozone into a respective plurality of diverted waterportions of streams prior to charging each portion into a respectiveballast tank of a plurality of ballast tanks.